addition of a draggable option for infiniteline

examples/plottingItems.py

@@ -18,7 +18,7 @@ pg.setConfigOptions(antialias=True)
 
 p1 = win.addPlot(title="Plot Items example", y=np.random.normal(size=100))
 inf1 = pg.InfiniteLine(movable=True, angle=90, label=True, textPosition=[0.5, 0.2], textColor=(200,200,100), textFill=(200,200,200,50))
-inf2 = pg.InfiniteLine(movable=True, angle=0, label=True, pen=(0, 0, 200), textColor=(200,0,0), bounds = [-2, 2], suffix="mm", hoverPen=(0,200,0))
+inf2 = pg.InfiniteLine(movable=True, angle=0, label=True, pen=(0, 0, 200), textColor=(200,0,0), bounds = [-2, 2], suffix="mm", hoverPen=(0,200,0), draggableLabel=True)
 inf3 = pg.InfiniteLine(movable=True, angle=45)
 inf1.setPos([2,2])
 inf1.setTextLocation(position=0.75)
@@ -26,7 +26,8 @@ inf2.setTextLocation(shift=0.8)
 p1.addItem(inf1)
 p1.addItem(inf2)
 p1.addItem(inf3)
-lr = pg.LinearRegionItem(values=[0, 10])
+
+lr = pg.LinearRegionItem(values=[5, 10])
 p1.addItem(lr)
 
 ## Start Qt event loop unless running in interactive mode or using pyside.

pyqtgraph/graphicsItems/InfiniteLine.py

@@ -32,7 +32,7 @@ class InfiniteLine(GraphicsObject):
 
     def __init__(self, pos=None, angle=90, pen=None, movable=False, bounds=None,
                  hoverPen=None, label=False, textColor=None, textFill=None,
-                 textPosition=[0.05, 0.5], textFormat="{:.3f}",
+                 textPosition=[0.05, 0.5], textFormat="{:.3f}", draggableLabel=False,
                  suffix=None, name='InfiniteLine'):
         """
         =============== ==================================================================
@@ -59,6 +59,9 @@ class InfiniteLine(GraphicsObject):
                         of the label from one side of the line to the other in the
                         orthogonal direction.
         textFormat      Any new python 3 str.format() format.
+        draggableLabel  Bool. If True, the user can relocate the label during the dragging.
+                        If set to True, the first entry of textPosition is no longer
+                        useful.
         suffix          If not None, corresponds to the unit to show next to the label
         name            name of the item
         =============== ==================================================================
@@ -81,6 +84,7 @@ class InfiniteLine(GraphicsObject):
         self.textColor = textColor
         self.textFill = textFill
         self.textPosition = textPosition
+        self.draggableLabel = draggableLabel
         self.suffix = suffix
 
         if (self.angle == 0 or self.angle == 90) and label:
@@ -190,17 +194,20 @@ class InfiniteLine(GraphicsObject):
             self._invalidateCache()
 
             if self.textItem is not None and self.getViewBox() is not None and isinstance(self.getViewBox(), ViewBox):
-                self.updateTextAndLocation()
-            else:
+                self.updateText()
+                if self.draggableLabel:
+                    GraphicsObject.setPos(self, Point(self.p))
+                else: # precise location needed
+                    GraphicsObject.setPos(self, self._exactPos)
+            else: # no label displayed or called just before being dragged for the first time
                 GraphicsObject.setPos(self, Point(self.p))
             self.update()
             self.sigPositionChanged.emit(self)
 
-    def updateTextAndLocation(self):
+    def updateText(self):
         """
-        Update the content displayed by the textItem and the location of the
-        item. Called only if a textItem is requested and if the item has
-        already been added to a PlotItem.
+        Update the content displayed by the textItem. Called only if a textItem
+        is requested and if the item has already been added to a PlotItem.
         """
         rangeX, rangeY = self.getViewBox().viewRange()
         xmin, xmax = rangeX
@@ -218,7 +225,8 @@ class InfiniteLine(GraphicsObject):
                 fmt = fmt + self.suffix
             self.textItem.setText(fmt.format(self.value()), color=self.textColor)
             posY = ymin+pos*(ymax-ymin)
-            GraphicsObject.setPos(self, Point(self.value(), posY))
+            #self.p = [self.value(), posY]
+            self._exactPos = Point(self.value(), posY)
         elif self.angle == 0:  # horizontal line
             diffMin = self.value()-ymin
             limInf = shift*(ymax-ymin)
@@ -231,7 +239,8 @@ class InfiniteLine(GraphicsObject):
                 fmt = fmt + self.suffix
             self.textItem.setText(fmt.format(self.value()), color=self.textColor)
             posX = xmin+pos*(xmax-xmin)
-            GraphicsObject.setPos(self, Point(posX, self.value()))
+            #self.p = [posX, self.value()]
+            self._exactPos = Point(posX, self.value())
 
     def getXPos(self):
         return self.p[0]
@@ -349,7 +358,7 @@ class InfiniteLine(GraphicsObject):
         self._invalidateCache()
 
         if self.getViewBox() is not None and isinstance(self.getViewBox(), ViewBox) and self.textItem is not None:
-            self.updateTextAndLocation()
+            self.updateText()
 
     def showLabel(self, state):
         """
@@ -387,6 +396,15 @@ class InfiniteLine(GraphicsObject):
         self.textPosition = [pos, shift]
         self.update()
 
+    def setDraggableLabel(self, state):
+        """
+        Set the state of the label regarding its behaviour during the dragging
+        of the line. If True, then the location of the label change during the
+        dragging of the line.
+        """
+        self.draggableLabel = state
+        self.update()
+
     def setName(self, name):
         self._name = name